Study of Rayleigh Lamb Wave Propagation in Elastic and Micropolar Solids

Abstract

The Classical theory of Elasticity is unable to explain the behaviour of the materials having complex micro structures such as polymers, porous media, fibers etc. To model such materials Eringen (1964) gave a theory which assumes that every particle of a material may do micro rotation in addition to macro translation. Researchers (Fischer (1982)), Fatemi et al.(2002) have even applied this theory to model the complex structures of bones. Lamb waves (1917), which propagate in solid plates with free boundaries, are elastic perturbations for which displacements occur both in the direction of wave propagation and perpendicular to the plane of plate. These waves are commonly used in ultrasonic Non Destructive Testing applications including material characterization of elastic plates (W.P.Rogers(1995)), bonding inspection (Wu and Liu(1999)), coating inspection (Lee and Cheng(2001)), defect inspection (Wu and Liu(1999)) and thickness measurement of thin films (W.P.Rogers(1995)). In the present work, a mathematical analysis has been done to study Lamb waves in Elastic and Micropolar plates.